When a single wireless device support two different types of radios that cannot use the wireless medium at the same time, the radio with the most flexibility in its communications opportunities must frequently try to use the wireless medium only during times when the other radio, whose communications opportunities may be more tightly scheduled by another device, is not using the medium. For example, in a single wireless device that supports both a WiFi radio and a WiMAX radio, the WiFi radio may have to try accessing the medium only when the WiMAX radio is not scheduled. However, if the WiFi radio requests too much time during its communication opportunities, it's more likely to have that request refused because it would interfere with the WiMAX radio's schedule. If the WiFi radio requests too little time, it must make more requests to communicate the necessary amount of data, and too much time will be lost to the overhead of acquiring the medium.